(1) Patient Ratio and Symptoms of Mycoplasma pneumoniae Pneumonia
Mycoplasma pneumoniae infections are classified as a community-acquired atypical pneumonia, and it is said that the proportion of Mycoplasma pneumoniae infections in community-acquired pneumonia amounts to 30 to 40% in adults and to even 60 to 70% when the adults are limited to young adults aged 15 to 25. The infection route of Mycoplasma pneumoniae is a respiratory tract infection, and it is not rare that such infections spread in facilities such as schools, and in families. In addition, in the Mycoplasma pneumoniae infections, pneumonia occurs in about 3 to 5% of the infections, and the remainder is bronchitis, upper respiratory tract inflammation, or inapparent infection. Characteristic symptoms include an obstinate cough that is not accompanied by expectoration from an early period of infection, and may be sometimes accompanied by symptoms such as fever, headache, pharyngeal pain, chills, or general malaise.
(2) Current Status of Screening for Mycoplasma pneumoniae infections
A screening test of the culture from a pharyngeal swab sample in patients and an antibody screening test using a patient's serum are common as screening tests for Mycoplasma pneumoniae infections. Since Mycoplasma pneumoniae per se grows only in a special culture medium, the culturing is difficult to execute, and it is necessary to perform a PCR test for the final identification of Mycoplasma pneumoniae, the culture screening can be carried out only in limited facilities, and this is a current status of the screening test of the culture. In addition, a screening test to quickly obtain the results has been demanded, because several weeks are needed for the culture.
On the other hand, because the antibody screening test is generally easy in the procedure and provides results more quickly compared to the screening test of the culture, such an antibody screening test is a test that has been well used. But there are problems such that it is difficult to determine whether the infection is a previous one or a current one because IgM antibody titers of Mycoplasma are long-lasting, and it takes a long time to increase the antibody titers. In order to solve the above problems, the judgment based on rise in the antibody titers between the acute phase of the infection and the convalescent phase of the infection over time is recommended, but since it takes a very long time to perform an antibody testing until the convalescent phase, therapy is delayed, so that its delay may cause prolongation and worsening of symptoms, as well as may cause the adverse effect of infection expansion due to secondary infection.
In addition, in order to solve the above problems, antibodies and detection methods for specifically detecting a microorganism belonging to Mycoplasma pneumoniae, which are useful for diagnosing Mycoplasma pneumoniae infections, have been disclosed.
For example, patent literature 1 describes an immunodetection method using a monoclonal antibody against a membrane protein antigen of Mycoplasma pneumoniae of about 43 kilodaltons (kDa). Also, patent literature 2 describes that detection of Mycoplasma pneumoniae can be performed with high accuracy by using an antibody against ribosomal protein L7/L12. In addition, patent literature 3 describes that a quick and specific diagnosis of Mycoplasma pneumoniae infection is possible by using a monoclonal antibody against protein P1 of Mycoplasma pneumoniae, the monoclonal antibody having a cross-reactivity of only 1% or less to other species of the genus Mycoplasma or other pathogenic species of coexisting flora.
However, in order to detect a microorganism belonging to Mycoplasma pneumoniae in clinical specimens, the antibody described above and the detection method using the antibody may require a complicated pretreatment of the specimens containing the microorganism, and have a problem such that they are insufficient for a specific diagnosis of Mycoplasma pneumoniae because of still low specificity and sensitivity.
(3) Mycoplasma genitalium and Diseases
Chlamydia trachomatis is known as the major causative bacteria of nongonococcal urethritis. However, Chlamydia trachomatis is detected in about 30 to 40% of patients with nongonococcal urethritis, and, in most cases, it is not clear where their symptoms originate. In addition to Chlamydia trachomatis, microorganisms of the genera Mycoplasma and Ureaplasma have attracted attention, and Mycoplasma genitalium in particular is shown as one of the causative bacteria of nongonococcal urethritis and sexually transmitted disease.
(4) Current Status of Screening for Mycoplasma genitalium Infections
Reports of Mycoplasma genitalium infections by the culture method or the PCR method have been published in papers, but since a quick diagnosis cannot be performed by these methods, a method for detecting quickly and specifically a microorganism belonging to Mycoplasma genitalium in clinical specimens has been demanded.